Reference

Web, Network & Privacy Glossary

Concise definitions for the terms used throughout WhatWebSees, with links to deeper guides and practical tools.

Addressing and networks

IP address: A numeric identifier used to deliver packets across IP networks. Read what an IP address can and cannot identify.
IPv4: The 32-bit Internet Protocol address format, commonly written as four decimal numbers such as 192.0.2.1.
IPv6: The 128-bit successor to IPv4, written in hexadecimal groups and designed with a vastly larger address space.
ASN: Autonomous System Number: an identifier for a network that announces routing information to other networks.
ISP / network provider: An organization that supplies network connectivity or originates an address range; it is not necessarily the website host or end user.
CIDR: Classless Inter-Domain Routing notation combines an address with a prefix length, such as /24. Try the subnet calculator.
Subnet: A contiguous IP address range described by a network prefix.
NAT: Network Address Translation rewrites addresses, commonly allowing many private devices to share one public IPv4 address.

DNS: The distributed naming system that maps domain names to typed records. See DNS record types explained.
Resolver: A service that performs DNS queries and caches answers for clients.
A record: Maps a DNS name to an IPv4 address.
AAAA record: Maps a DNS name to an IPv6 address.
CNAME: Makes one DNS name an alias of another canonical name.
MX: Lists mail exchangers for a domain, with preference numbers.
TXT: Carries text values used for purposes such as verification and email policy.
NS: Identifies authoritative name servers for a zone.
SOA: The Start of Authority record containing zone authority and timing fields.
PTR: Maps an IP address in reverse DNS to a hostname.
Reverse DNS: A lookup from an address to its optional PTR name. Use the reverse DNS checker.
TTL: Time To Live: how long a DNS response may normally remain cached.
DNSSEC: Extensions that authenticate DNS data with digital signatures; they do not encrypt queries. Read the DNSSEC guide.
DNSKEY: A public key record used to verify signatures in a DNS zone.
DS: Delegation Signer record placed in a parent zone to link a child’s key into the DNSSEC chain of trust.

SPF: A DNS policy describing which systems may send mail for a domain in the SMTP envelope.
DKIM: A message signature mechanism whose public verification key is published under a DNS selector.
DMARC: A policy and reporting layer requiring alignment with SPF or DKIM for the visible From domain. See how all three fit together.

HTTP: The application protocol used for requests and responses on the web.
HTTPS: HTTP carried over an authenticated TLS connection.
TLS: Transport Layer Security, which encrypts data in transit and authenticates the server certificate.
SSL: The obsolete predecessor to TLS; “SSL certificate” remains a common informal name for a TLS certificate.
Certificate: A signed document binding a public key to names and validity dates.
CA: Certificate Authority: an entity trusted to issue or sign certificates under defined rules.
SNI: Server Name Indication communicates the intended hostname during TLS setup so a server can select the right certificate.
HTTP header: A named metadata field in an HTTP request or response. Read HTTP headers explained.
HSTS: A response policy asking browsers to use HTTPS for a host for a specified time.
CSP: Content Security Policy, which restricts permitted sources and behaviors for page resources.
Redirect: A 3xx response that points the client to another URL using Location. Inspect a chain with the redirect checker.

User-Agent: A request header describing the browser family and platform, often with compatibility tokens.
Client Hints: Structured browser-provided request fields that can communicate selected device or browser characteristics.
WebGL: A browser graphics API that can expose renderer and capability information.
Canvas fingerprint: A value derived from rendered canvas pixels; consistency can contribute a signal but is not personal identification.
Browser fingerprint: A combination of observable attributes used to distinguish or group browsers without a traditional cookie.
Cookie: A small value a site asks a browser to return on later matching requests.
GPC: Global Privacy Control, a browser signal expressing a request not to sell or share personal data in applicable contexts.
Punycode: An ASCII encoding used within internationalized domain names; non-ASCII labels commonly begin xn--.
RDAP: Registration Data Access Protocol: structured HTTPS access to public registry data. Try the RDAP lookup.
robots.txt: A public origin file containing crawler directives; it is not authentication and is not the same as noindex.
XML sitemap: A machine-readable list of canonical URL candidates or nested sitemap documents offered for discovery.